1. Field of the Invention
The present invention is in the field of particulate material handling, and specifically relates an apparatus that is attached to the outlet of a hopper to assist and control the discharge of particulate material onto the loading surface of a feeder, such as a moving belt, so that an uninterrupted controlled flow will be obtained with a considerable reduction in the power required to drive the feeder, compared to the prior art.
2. The Prior Art
In a hypothetical and impractical situation, no interface would be used. The particulate material would stream from the outlet of the hopper, would become airborne, and would land on a moving belt which would transport it to a truck, a railroad car, or a pile. Such a technique would require an oversized feeder which would be only lightly loaded and hence operating at very low efficiency. Also, there would be no control over the discharge rate.
To improve the efficiency and controllability of the system, workers in the art discovered that it was advantageous to provide an interface between the outlet of the hopper and the feeder. Such an interface could serve to control the lateral dispersion of the particulate material and to reduce the effect of cross winds. With reduced lateral dispersion, narrower feeders were used and these were more heavily loaded and hence more efficient.
Normally when an interface is used, the body of particulate material extends without interruption from inside the hopper, downward through the hopper outlet and through the interface to the loading surface of the feeder.
Since the particles within the hopper outlet have no velocity in the direction of travel of the feeder, while the particles bearing against the loading surface of the feeder necessarily have a moderate velocity, it follows that the feeder produces a shearing effect in the body of particulate material. In fact, typically, the power supplied to the feeder is largely used to overcome the shearing resistance, and a smaller component of the power is used to overcome friction and to accelerate the particulate material. The frictional component is related to the downward pressure on the feeder loading surface.
Until the present invention, it was believed that little could be done to reduce the shear component or the frictional component of the power required to operate the feeder. Progress in reducing the required feeder power was at a standstill until, in the mind of the present inventor, there arose some remarkable insights that will now be described.